Continuity mistake: When Carl gets shot, and we see him in the ground, not only does the blood spot on his short change in the next shot of him on the ground, but he's in a completely different shirt. It's still a cameo shirt, but the cameo pattern is different.
Bloodletting - S2-E2
Continuity mistake: When T-Dog is telling Dale that all he found was ibuprofen and cigarettes, he is holding his hand up and they are both looking at each other. In the next shot, suddenly his arm is down and they are both looking forward. (00:22:44)
Chupacabra - S2-E5
Continuity mistake: Daryl ripped off his shirt to wrap around his wound, and was left in only his vest. Except, a shot later, he's seen wearing his shirt again, cutting off the walker's ears. (00:25:30)
Chupacabra - S2-E5
Continuity mistake: During the scene where Norman Reedus is talking to Michael Rooker, watch the dirt and sand around Reedus' mouth appear and disappear during the talk while he is on his back.
Pretty Much Dead Already - S2-E7
Continuity mistake: As Daryl and Shane argue near the start, Daryl's movements don't correspond with the changing shots: one moment he is standing in front of Carol, then he is standing by her, then he has moved closer to Rick - all within the same one-liners. As his argument with Shane grows, he again is standing by Carol, or closer, near Rick. At one point, a shot shows Daryl about to lounge at Shane, as Rick blocks him, but the very next shot shows him right next to Carol, who at that point would have been standing behind Rick. (00:10:00 - 00:11:00)
Pretty Much Dead Already - S2-E7
Continuity mistake: After Carol tells Shane they are not leaving without finding Sophia, Daryl enters and reminds Shane about the doll he found down at the swamp earlier, and they start to argue. During this he crosses front to Carol's right. In the very next shot Daryl is suddenly shown standing in the same spot as prior, next to Carol. (00:10:00)
Pretty Much Dead Already - S2-E7
Continuity mistake: Rick is talking with Hershel in his kitchen and asks him to please not send Them out into the world again. Hershel is looking down at his sink from the side angle. When it cuts to a view from behind, he's suddenly looking up to the left out of the window, only to lower his head back down towards the sink again. (00:13:57)
Pretty Much Dead Already - S2-E7
Continuity mistake: After talking with Hershel, Rick heads out to the barn and meets up with Shane at a tractor. Shane asks him which way is it going to go as Rick is looking to his left down at the tractor. When the shot cuts to The Other Side as Rick responds, he's suddenly looking straight ahead at the barn. (00:15:32)
Pretty Much Dead Already - S2-E7
Continuity mistake: Deleted footage/special release only: Carol confronts Daryl about the boy being held hostage inside the barn (following Sophia's death), reasoning with him about pretending not to care when he truly does. At one point he moves to her, almost in her face. However, the following shot shows only a close up of Carol, implying they are standing feet apart, which is not the case. (00:24:10)
Pretty Much Dead Already - S2-E7
Continuity mistake: As the group kills the walkers that come out of the barn, the camera shows several different vantage points from in front of the barn, inside of the barn etc., it shows the walkers lying with a clear path between them, and in another it shows the walkers lying in a jumbled pile with no path between them. This goes back and forth a few times until Sophia comes out of the barn, and there is no clear path again.
Pretty Much Dead Already - S2-E7
Continuity mistake: When Shane finds Dale in the swamp trying to hide the guns, when he first sees Dale, Dale is holding a large spike to drive into the tree. In the next second they show Dale standing next to the tree with the spike already in it.
Continuity mistake: In Season 2 episode 7, "Pretty Much Dead Already," at the end where Rick shoots the walker Sophia, she falls to her right. In the next episode, "Nebraska," picking up immediately after the last, she is in an entirely different position, as if she fell forward.
Continuity mistake: Rick tells Hershel to cover Glenn. And as he's telling him to see if he can make it to his car, Hershel isn't looking at Rick, but straight ahead deeper into the bar. When the camera cuts to a different angle, suddenly Hershel is looking right at Rick. (00:13:55)
Continuity mistake: At the crossroads, after Rick starts to walk away from Shane, Shane starts to tell the story of what happened with the outbreak. Rick pauses and is looking off to his right as he is in the blurry foreground with Shane talking behind him, looking towards the left of camera. The angle cuts to a view from behind Rick, and suddenly Rick has his head turned to his left now, but also towards the left of camera but from this angle. (00:16:43)
Continuity mistake: Towards the end when Rick and Shane are leaning up against the car, Rick says it can't be that easy killing anyone, you know that. Shane is looking ahead with his head angled down in that shot, but when the camera cuts to a different angle, Shane is holding his head up right. (00:40:15)
Beside the Dying Fire - S2-E13
Continuity mistake: When the farm is overrun, the tires on Daryl's motorcycle are offroad tires. Later in the episode however, these tires change magically to smoother street tires. (00:15:35 - 00:28:40)
When the Dead Come Knocking - S3-E7
Continuity mistake: The first shot of Maggie waiting for the Governor to enter shows her wearing a black tank top with her shoulders bare. After he cuts the duct tape around her wrists, the camera pans up and she now has black bra straps showing on her shoulders. (00:26:10)
When the Dead Come Knocking - S3-E7
Continuity mistake: The Governor takes off his gun belt while interrogating Maggie, and a few shots later has it on again in the same scene.
Continuity mistake: The previous episode ended with Rick and his group reaching Woodburry and it was dark. This episode starts with Tyreese and his group reaching the prison in the daylight, and being rescued by Carl and brought back to their cell block. If you look at the windows it is still light out, they have no electricity so it can't be exterior lighting, yet in the scene before and after this, Rick and his group are at the Woodburry at nighttime.
Answer: Walkers are attracted to noise, they can tell who's dead and who isn't dead, in S1 when Rick and Glenn cover themselves in walkers' guts they're able to get far by walking through the herd of walkers because they smell like they're dead, but as soon as the guts get washed off by the rain the walkers immediately attack them, if you draw attention to yourself they will attack you which we've seen that many times throughout the series that it's not always successful. Whether you're covered in guts hiding under dead corpses or under a car.